1. Field of the invention
The resent invention relates to a photographic lens system, and, more particularly, to a wide angle lens system suitable for use with a lens shutter camera.
2. Description of Related Art
Much attention has been given to various optical approaches relating to miniaturization of still cameras equipped with wide angle lens systems. Various efforts have been made to provide wide angle lens systems having large F numbers and well corrected aberrations.
One such a wide angle lens system is that described in Japanese Unexamined Patent Publication No. 58-4112.
While the wide angle lens system has an angle of view of 56 degrees and an F number of approximately 2.0 and is well corrected for various aberrations, nevertheless, various constraints must be imposed upon the overall camera size. For example, since the wide angle lens system is intended to be used with single lens reflex cameras and consequently, has a long back focal distance, it must have a long overall length (which is a distance from the foremost surface of the lens system to a focal point) which is undesirable for miniaturized or compact cameras. Together, the angle of view of approximately 56 degrees is somewhat narrow for lens shutter cameras.
Another wide angle lens system, described in, for instance, Japanese Unexamined Patent Publication No.5-164961, has a wide angle of view of 63 degrees and an F number of 2.0. This wide angle lens is designed for use with lens shutter cameras so as to have a sufficient space for installation of a lens shutter and well corrected for sagittal come which is generally caused by surfaces on opposite sides of the lens shutter.
This wide angle lens system has an overall length approximately 1.4 times as long as its focal length, rendering a camera difficult to be made compact. Further, though the wide angle lens system is well corrected for sagittal coma, it still has large aberrations, such as astigmatism and distortion, and consequently is not said to be well collected for aberrations as a whole.